Big Data Analytics

Following figure shows the key differences between OLAP and DataWarehousing Environments

One major difference between the types of system is that data warehouses are notusually in third normal form (3NF), a type of data normalization common in OLTPenvironments.

Data warehouses and OLTP systems have very different requirements. Here are someexamples of differences between typical data warehouses and OLTP systems:■ WorkloadData warehouses are designed to accommodate ad hoc queries. You might notknow the workload of your data warehouse in advance, so a data warehouseshould be optimized to perform well for a wide variety of possible queryoperations.OLTP systems support only predefined operations. Your applications might bespecifically tuned or designed to support only these operations.■ Data modificationsA data warehouse is updated on a regular basis by the ETL process (run nightly orweekly) using bulk data modification techniques. The end users of a datawarehouse do not directly update the data warehouse.In OLTP systems, end users routinely issue individual data modificationstatements to the database. The OLTP database is always up to date, and reflectsthe current state of each business transaction.■ Schema designData warehouses often use denormalized or partially denormalized schemas (suchas a star schema) to optimize query performance.OLTP systems often use fully normalized schemas to optimizeupdate/insert/delete performance, and to guarantee data consistency.■ Typical operationsA typical data warehouse query scans thousands or millions of rows. For example,"Find the total sales for all customers last month."A typical OLTP operation accesses only a handful of records. For example,"Retrieve the current order for this customer."■ Historical dataData warehouses usually store many months or years of data. This is to supporthistorical analysis.OLTP systems usually store data from only a few weeks or months. The OLTPsystem stores only historical data as needed to successfully meet the requirementsof the current transaction.